1. Field of the Invention
The present invention relates to a keyboard apparatus for an electronic musical instrument including hammers each of which acts to add inertia to a key depressing operation when pivoted by being actuated by a depressed key.
2. Description of the Related Art
Conventionally, there is known a keyboard apparatus for an electronic musical instrument in which each hammer having an appropriate mass is pivoted upon key depression operation, to attain a natural key depression feeling similar to that of an acoustic piano (Japanese Patent Publication No. 3060930).
In this keyboard apparatus, each hammer includes a resin hammer base supported for pivotal motion by a frame and an elongated member of an appropriate mass extending rearwardly therefrom. Upon key depression operation, an actuating portion of the depressed key actuates an actuated portion of the corresponding hammer, whereby the hammer is pivoted in conjunction with the key depression operation, with a free end of the elongated member vertically swung. The elongated member of the hammer is formed by a solid metal rod having a rear half thereof folded back forward, and fixed at its one end to the hammer base, for example, by means of outsert molding. The inertia imparted to the key depression operation is mainly based on the mass of the elongated member.
In a keyboard apparatus of this type, if the elongated member of the hammer is low in rigidity (in particular, low in the second moment of area), undesired vibration is produced when the elongated member is in contact with a stopper for restricting a key depression end position. In that case, an adverse effect can be produced on a feeling at the completion of key depression, or the elongated member can be deformed during a long-term use thereof to vary a key depression stroke. It is therefore preferable that the elongated member be designed to have an increased rigidity as much as possible.
To increase the rigidity of the elongated member, it may be, for example, thickened to increase the sectional area thereof. On the other hand, the mass of the elongated member directly affects the inertia force added to the key, and therefore, increasing the sectional area of the elongated member cannot always be appropriate solution to attain the desired inertia. In other words, there is a restriction in increasing the rigidity of the elongated members, posing a problem.